For the primary tests and summary diagrams we overclocked our six-core processor with the clock generator frequency set at 125 MHz, the multiplier at 35x and “Load-Line Calibration” enabled to 4.375 GHz. The nominal processor Vcore was increased to 1.385 V in the mainboard BIOS. After that we tested the new cooling systems at even higher frequency and voltage settings. Turbo Boost was disabled during this test session, and Hyper-Threading technology was enabled to increase the heat dissipation. The memory voltage was at 1.65 V and its frequency was 2000 MHz with 9-11-10-28 timings. All other parameters available in the mainboard BIOS and related to CPU or memory overclocking remained unchanged.

All tests were performed under Windows 7 Ultimate x64 SP1 operating system. We used the following software during our test session:

The CPU was loaded with two consecutive LinX AVX test runs with the settings as indicated above. The stabilization period for the CPU temperature between the two test cycles was about 8-10 minutes. We took the maximum temperature of the hottest CPU core for the results charts. Moreover, we will also provide a table with the temperature readings for all cores including their average values.

The ambient temperature was checked next to the system case with an electronic thermometer with 0.1 °C precision that allows hourly monitoring of the temperature changes over the past 6 hours. The room temperature during our test session varied between 23.0-23.5°C.

The noise level of each cooler was measured between 1:00 and 3:00 AM in a closed room about 20 m2 big using CENTER-321 electronic noise meter. The noise level for each cooler was tested outside the system case when the only noise sources in the lab were the cooler and its fan. The noise meter was installed on a tripod and was always at a 150 mm distance from the cooler fan rotor. The tested cooling systems were placed at the edge of the desk on a sheet of polyurethane foam. The lowest noise reading our noise meter device can register is 29.8 dBA and the subjectively comfortable noise level in these testing conditions was around 36 dBA (do not mistake it for the low noise level). The fan(s) rotation speed was adjusted in the entire supported range using our in-house controller by changing the voltage with 0.5 V increment.

Just like all the previously reviewed cooling systems, the new NZXT Kraken X40 will compete against the best air cooler out there - Phanteks PH-TC14PE. However, instead of the two default fans that are not particularly quiet we topped Phanteks heatsink with two Corsair AF140 fans:

According to our preliminary tests, this modifications barely has hardly affected the cooling efficiency of this cooler, but has dramatically improved its acoustic performance. Nevertheless, the noise graph below will also have the curve for the Phanteks PH-TC14PE with the default fans for your reference.

Besides the super-cooler, NZXT Kraken X40 will also compete against the best closed-loop liquid-cooling system of all we have tested so far – Corsair H100i Extreme Performance:

As you can see, this system was tested in identical conditions as NZXT Kraken X40 and not inside the system case. I would like to add that the rotation speed of all fans was controlled using our special in-house controller with ±10 RPM precision.